To continue the investigation of the mechanisms by which testosterone regulates the differentiation, growth, and function of the male genital tract and the exploration of the pathogenetic mechanisms by whih derangements of this system eventuate, a variety of experiments have been projected. These include a characterization and purification of the nuclear testosterone binding protein of rat prostate, a study of the regulation of the 5 alpha reductase enzyme that converts testoterone to dihydrotestosterone, studies of the pathogenesis of male pseudohermaphroditism in mouse embryos and in man, an investigation of the role of dihydrotestosterone in the development of benign prostatic hypertrophy in the dog, an analysis of the role of dihydrotestosterone formation in regulating the growth of human prostatic carcinoma, an analysis of the physiology of androgen mediated growth of hair in man, an investigation of the androgen regulation of embryonic development of the external genitalia, and a study of the regulation of embryonic testicular function.